"The greatest crisis facing us is a crisis in the organization and accessibility of human knowledge. We own an enormous 'encyclopedia' which isn't even arranged alphabetically. Our 'file cards' are spilled on the floor. The answers we want may be buried somewhere in the heap."         --Robert Heinlin

CANNON'S LAW of DENERVATION SUPERSENSITIVITY



Walter B. Cannon was an intellectual giant and one of the world's preeminent physiologists of the first half of the 20th century. Harvard Professor and Chairman of the Department of Physiology (1906-1942), he is credited with first coining the terms 'fight or flight response' and 'homeostasis'. His additional scientific research on 'denervation supersensitivity' at the end of his career was never published directly in the medical literature. (The title page of this research as seen above was published posthumously in the lay press by MacMillan in 1949).

This now well-established but generally under-appreciated principle of physiology is aptly known as 'Cannon's Law of Denervation Supersensitivity'. It describes the wide ranging effects of the complete loss of nerve inputs to a variety of bodily structures under experimental conditions. One of the many responses to nerves that are sick or dysfunctional (now termed Disuse Supersensitivity) is that  the muscles that are supplied by these nerves shorten and tighten (due to the supersensitivity of both the muscle's specialized stretch receptors and motor nerve-muscle junctions), resulting not only in muscle spasm and stiffness which limit flexibility, but a whole sequence of pain compounding reactions. The two earliest are that localized taut bands of muscle fibers begin to compress the small specialized pain sensing (and now extra-sensitive) nerve fibers within the muscle (known as myofascial tender or trigger points) causing type 1 pain, and the compressed muscles do not allow proper blood flow in, or waste products to be removed. This leads to a build up of lactic acid, which further enhances the perception of pain through type 2 pain mechanisms. Continued and prolonged muscle shortening or contracture gradually leads to increased mechanical tension on the muscle's tendonous attachments to bone, causing all of the various tendonitis (types 1 & 2 pain) syndromes throughout the body. The end result is a truly vicious snowballing cycle of pain, with the muscle shortening further increasing pressure on the nerves.